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\section{Concept}
\begin{itemize}
    \item Explain complement of variable A, literals, product/implicant, minterm, maxterm.

    \item In logic digital design,Why bother simplifying a Boolean equation if it remains logically
          equivalent?

    \item How can we measure delay between an input change and the consequense output change?

    \item What is rising edge?What is falling edge?
    \item There're two kinds of delays,the propagation delay and the contamination delay.Expain what they are.
\end{itemize}



\section{Concept Answers}
\begin{itemize}
    \item complement of variable A:A's inverse $\overline{A}$. \\
          literal:a variable and its complement \\
          product/implicant:the AND of one or more literals\\
          minterm:a product involving all of the inputs to the function\\
          sum:the OR of one or more literals\\
          maxterm:a sum involving all of the inputs to the function\\
          \\
          For example,a minterm is $A\overline{B}\overline{C}$.A maxterm is $A+\overline{B}+\overline{C}$

    \item Simplifying reduces the number of the gates used to physically implement the function.\\
          It makes our circuit smaller,cheaper and faster.
    \item  We measure delay from the 50\% point of the input
          signal, A, to the 50\% point of the output signal, Y. The 50\% point is the
          point at which the signal is half-way (50\%) between its LOW and HIGH
          values as it transitions.
    \item the transition from LOW to HIGH/the transition frome HIGH to LOW
    \item The propagation delay $t_{pd}$ is the maximum time
          from when an input changes until the output or outputs reach their final
          value. The contamination delay $t_{cd}$ is the minimum time from when an
          input changes until any output starts to change its value.
\end{itemize}


\section{Inteview Questions From Book}
\begin{itemize}
    \item Sketch a schematic for the two-input XOR function using only NAND gates. How few can you use?
    \item Design a circuit that will tell whether a given month has 31 days in it.
          The month is specified by a 4-bit input $A_{3:0}$. For example, if the inputs are 0001,
          the month is January, and if the inputs are 1100, the month is December. The
          circuit output Y should be HIGH only when the month specified by the inputs has
          31 days in it. Write the simplified equation, and draw the circuit diagram using a
          minimum number of gates. (Hint: Remember to take advantage of don’t cares.)
    \item What is a tristate buffer? How and why is it used?
    \item A gate or set of gates is universal if it can be used to construct any
          Boolean function. For example, the set {AND, OR, NOT} is universal. \\
          (a) Is an AND gate by itself universal? Why or why not?\\
          (b) Is the set {OR, NOT} universal? Why or why not?\\
          (c) Is a NAND gate by itself universal? Why or why not?   \\
    \item Explain why a circuit’s contamination delay might be less than
          (instead of equal to) its propagation delay.

\end{itemize}







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